1. Field of the Invention
The present invention relates to a polishing apparatus used in a working semiconductor device, and more particularly, to a polishing apparatus which can automatically perform processes including wafer polishing, washing, and drying.
2. Information of the Related Art
A polishing apparatus is an apparatus which presses a wafer against an abrasive cloth attached to a base, for example, thereby working the wafer so that it has a specular surface. The single-sided polishing technique, which has conventionally been used in semiconductor manufacturing processes, is applied to the modern field of working semiconductor devices. This applied technique is called a chemical mechanical polishing (CMP) technique, and polishing apparatuses which use this technique are called CMP apparatuses.
Conventionally, many of the polishing apparatuses of this type have no cleaning-drying device therein. Normally, in these apparatuses, polished wafers are stored in a cassette in a separately provided water tank. In cleaning and drying the wafers, an operator takes the device out of the water tank, and carries them to a cleaning-drying device. In one such conventional polishing apparatus, a base section on which each wafer is held by means of a top ring is polished, a loader section for attaching and detaching the wafer, and a cleaning section for cleaning the surface of the top ring are arranged in different positions, and the top ring is moved between these three positions of operation. The apparatus may also comprise exclusive-use devices for centering and reversing the wafer in mounting it on the top ring, for example.
According to the conventional CMP apparatuses arranged in this manner, centering and reversing the wafer require the exclusive-use devices, and frequent rotating operation of the top ring entails extra machining time. Since the polishing apparatus is arranged independently of the cleaning-drying device, moreover, dripping during transportation or the like makes it hard to set the CMP apparatus in a clean room, so that the production line is complicated.
Since plenty of particles are produced when wafers are polished by means of the polishing apparatus of this type, the apparatus cannot be installed in an ordinary clean room. Accordingly, the conventional polishing apparatus is set in a separate room whose cleanness is lower than that of the normal clean room. In this arrangement, the wafers in the clean room are carried into the separate room, worked and cleaned by means of the polishing apparatus, and then returned to the clean room to start the next stage.
If the polishing apparatus is set in the separate room in this manner, the general flow of the semiconductor manufacturing processes stagnates during the use of the polishing apparatus, thus constituting a substantial hindrance to the automation of the manufacturing processes. Also, the use of the separate room entails extra costs, and besides, each wafer must be cleaned every time it is delivered from the low-cleanness separate room into the high-cleanness clean room.